Linezolid resistance in Mycobacterium tuberculosis isolates at a tertiary care centre in Mumbai, India.

Background & objectives: Linezolid (LZD) is increasingly being used in tuberculosis (TB) treatment. However, LZD resistance has already been reported, which is highly alarming, given its critical therapeutic role. This study was aimed to phenotypically and genotypically assess LZD resistance in Mycobacterium tuberculosis (MTB) isolates at a laboratory in a tertiary care centre in Mumbai, India. Methods: A sample of 32 consecutive LZD-resistant MTB isolates identified by liquid culture susceptibility testing was subjected to whole-genome sequencing (WGS) on the Illumina NextSeq platform. Sequences were analyzed using BioNumerics software to predict resistance for 12 antibiotics within 15 min. Results: Sixty eight of the 2179 isolates tested for LZD resistance by MGIT-based susceptibility testing (June 2015 to June 2016) were LZD-resistant. Thirty two consecutive LZD-resistant isolates were analyzed by WGS to screen for known mutations conferring LZD resistance. WGS of 32 phenotypically LZD-resistant isolates showed that C154R in the rplC gene and G2814T in the rrl gene were the major resistance determinants. Interpretation & conclusions: LZD resistance poses an important risk to the success of treatment regimens, especially those designed for resistant isolates; such regimens are extensively used in India. As LZD-containing regimens increase in prominence, it is important to support clinical decision-making with an improved understanding of the common mutations conferring LZD resistance and their frequency in different settings.

Performance of bioMérieux Lowenstein-Jensen slopes in plastic tube packaging, compared to existing phenotypic methods, for efficient recovery of the Mycobacterium tuberculosis complex.

PURPOSE: Lowenstein-Jensen (LJ) medium used for cultivating Mycobacterium tuberculosis (MTB) is marketed in glass packaging. Breakage of glass slope is a major biosafety risk, especially during processing and storage, which gets magnified in large laboratories. We evaluated the performance of new bioMérieux (bMx) LJ slopes in plastic packaging, compared to bMx glass LJ medium and Becton Dickinson Mycobacterial Growth Indicator Tube (MGIT), for MTB recovery. METHODOLOGY: Consecutive pulmonary/extra-pulmonary samples (n=240) were processed using routine methods of decontamination, inoculation and incubation. RESULTS: Plastic LJ slopes detected all 213 true-positive cases. The mean time-to-growth detection was 17.97 days for plastic LJ slopes, compared to 18.08 and 13.53 days for glass LJ slopes and MGIT, respectively. No statistically significant difference was observed between the two LJ slopes (P< 0.05). Both LJ slopes had a sensitivity and specificity of 100%, with respect to MGIT. CONCLUSION: Plastic LJ slopes are a good alternative to the traditional glass slopes. The medium quality did not differ with the packaging material. Increased surface area of these slants allowed enhanced growth, and the clear plastic material allowed accurate recording of growth. The wide mouth of these containers eased inoculation. Increased biosafety, by elimination of breakage risk, is the biggest advantage of this modification.

Evaluation of pyrosequencing for extensive drug resistance-defining anti-tuberculosis drugs for use in public healthcare.

MGIT 960 drug susceptibility testing (DST) for Mycobacterium tuberculosis was compared for performance and speed with pyrosequencing (PSQ). Pulmonary samples (n = 100), from GeneXpert/MTB/Rifampicin-resistant patients receiving second-line treatment for 1-3 months, were subjected to DST and PSQ for seven drugs (isoniazid, rifampicin, kanamycin, amikacin, capreomycin, moxifloxacin, and ofloxacin). The mean time-to-result was 35 and two days for DST and PSQ, respectively. Average concordancy was 92.7%. Theoretically, PSQ showed substantial incremental value over the commercial Genotype MTBDRplus/sl. Mutations not considered in commercial molecular tests were observed by PSQ. Our findings corroborated the association between S315T (katG region) and S531L (rpoB region) and phenotypic resistance. PSQ is more rapid, can be performed from the sample, provides information about all known mutations simultaneously, allows extensive post-processing analyses, and is open to the inclusion of new mutations. It indicates the exact mutation conferring resistance to the particular drug, unlike the qualitative DST.

Evaluation of OMNIgene®â€¢SPUTUM for tuberculosis sample processing and liquid culture at a hospital laboratory in India.

This preliminary evaluation examined the reagent OMNIgene®â€¢SPUTUM (OM-S) as a tool to eliminate NaOH/NALC processing prior to Middlebrook liquid culture for Mycobacterium tuberculosis (MTb). Twenty-seven manually split samples (OM-S-treated vs. NaOH/NALC) showed 100% agreement: 81.5% MTb-positive and 18.5% MTb-negative. On average, OM-S-treated specimens required 1.2 additional days to culture positivity.